The object of this proposal will be to measure the tissue histamine concentration present in the albino rabbit's eye. Also, tissue levels of histamine between the optic nerve and iris will be measured to see if the concentration varies with the mast cell population's variation of cell density through this region. Change in histamine tissue levels will be evaluated following histamine release by inflammation and by a histamine releasingg agent. A fluorometric technique will be used to determine the tissue histamine.